Mg-gallate metal-organic framework-based sprayable hydrogel for continuously regulating oxidative stress microenvironment and promoting neurovascular network reconstruction in diabetic wounds

Chronic diabetic wounds are the most common complication for diabetic patients. Due to high oxidative stress levels affecting the entire healing process, treating diabetic wounds remains a challenge. Here, we present a strategy for continuously regulating oxidative stress microenvironment by the catalyst-like magnesium-gallate metal-organic framework (Mg-GA MOF) and developing sprayable hydrogel dressing with sodium alginate/chitosan quaternary ammonium salts to treat diabetic wounds. Chitosan quaternary ammonium salts with antibacterial properties can prevent bacterial infection. The continuous release of gallic acid (GA) effectively eliminates reactive oxygen species (ROS), reduces oxidative stress, and accelerates the polarization of M1-type macrophages to M2-type, shortening the transition between inflammation and proliferative phase and maintaining redox balance. Besides, magnesium ions adjuvant therapy promotes vascular regeneration and neuronal formation by activating the expression of vascular-associated genes. Sprayable hydrogel dressings with antibacterial, antioxidant, and inflammatory regulation rapidly repair diabetic wounds by promoting neurovascular network reconstruction and accelerating re-epithelialization and collagen deposition. This study confirms the feasibility of catalyst-like MOF-contained sprayable hydrogel to regulate the microenvironment continuously and provides guidance for developing the next generation of non-drug diabetes dressings.

Bioactive citrate-based polyurethane tissue adhesive for fast sealing and promoted wound healing

As a superior alternative to sutures, tissue adhesives have been developed significantly in recent years. However, existing tissue adhesives struggle to form fast and stable adhesion between tissue interfaces, bond weakly in wet environments and lack bioactivity. In this study, a degradable and bioactive citrate-based polyurethane adhesive is constructed to achieve rapid and strong tissue adhesion. The hydrophobic layer was created with polycaprolactone to overcome the bonding failure between tissue and adhesion layer in wet environments, which can effectively improve the wet bonding strength. This citrate-based polyurethane adhesive provides rapid, non-invasive, liquid-tight and seamless closure of skin incisions, overcoming the limitations of sutures and commercial tissue adhesives. In addition, it exhibits biocompatibility, biodegradability and hemostatic properties. The degradation product citrate could promote the process of angiogenesis and accelerate wound healing. This study provides a novel approach to the development of a fast-adhering wet tissue adhesive and provides a valuable contribution to the development of polyurethane-based tissue adhesives.

Design and fabrication of high-performance injectable self-setting trimagnesium phosphate

Magnesium phosphate bone cement has become a widely used orthopedic implant due to the advantages of fast-setting and high early strength. However, developing magnesium phosphate cement possessing applicable injectability, high strength, and biocompatibility simultaneously remains a significant challenge. Herein, we propose a strategy to develop high-performance bone cement and establish a trimagnesium phosphate cement (TMPC) system. The TMPC exhibits high early strength, low curing temperature, neutral pH, and excellent injectability, overcoming the critical limitations of recently studied magnesium phosphate cement. By monitoring the hydration pH value and electroconductivity, we demonstrate that the magnesium-to-phosphate ratio could manipulate the components of hydration products and their transformation by adjusting the pH of the system, which will influence the hydration speed. Further, the ratio could regulate the hydration network and the properties of TMPC. Moreover, in vitro studies show that TMPC has outstanding biocompatibility and bone-filling capacity. The facile preparation properties and these advantages of TMPC render it a potential clinical alternative to polymethylmethacrylate and calcium phosphate bone cement. This study will contribute to the rational design of high-performance bone cement.

A Gelatin-Based Composite Hydrogel with a "One Stone, Two Birds" Strategy for Photothermal Antibacterial and Vascularization of Infected Wounds

Bacterial infection, prolonged inflammation, and insufficient angiogenesis are the main challenges for effective wound repair. In this work, we developed a stretchable, remodeling, self-healing, and antibacterial multifunctional composite hydrogel for infected wound healing. The hydrogel was prepared using tannic acid (TA) and phenylboronic acid-modified gelatin (Gel-BA) through hydrogen bonding and borate ester bonds and incorporated iron-containing bioactive glasses (Fe-BGs) with uniform spherical morphologies and amorphous structures to achieve GTB composite hydrogels. On one hand, the chelation of Fe³⁺ in Fe-BGs with TA endowed the hydrogel with good photothermal synergistic antibacterial ability; on the other hand, the bioactive Fe³⁺ and Si ions contained in Fe-BGs can recruit cells and synergistically promote blood vessel formation. In vivo animal experiments showed that the GTB hydrogels remarkably accelerated infected full-thickness skin wound healing by improving granulation tissue formation, collagen deposition, and the formation of nerves and blood vessels while decreasing inflammation. This hydrogel with a dual synergistic effect and ″one stone, two birds″ strategy holds immense potential for wound dressing applications.

Resource Support for "Mobilization-Participation" in Public Health Emergencies Based on a Complex Network Evolutionary Game

The organized system of emergency resources with the participation of social subjects features a network, which puts forward new requirements for mobilization policies for public health emergencies. Considering the "mobilization-participation" action of the relationship between the government and social resource subjects and revealing the mechanism of governance measures represent the foundation of developing effective mobilization strategies. To analyze the behavior of subjects in an emergency resource network, this study proposes a framework for the emergency actions of government and social resource subjects, as well as clarifies the functions of relational mechanisms and interorganizational learning in decision making. The game model and its rules of evolution in the network were developed by considering the interventions of rewards and penalties. An emergency resource network was constructed on the basis of a response to the COVID-19 epidemic in a city in China, and a simulation of the "mobilization-participation" game was designed and conducted. We propose a path to promote emergency resource actions by analyzing the initial situations and the interventions' effects. This article suggests that guiding and improving the initial selection of subjects under a certain reward system would be an effective path to facilitate resource support actions during public health emergencies.

Exploring time evolution characteristics of the collaborative mode in emergency information release of public health emergencies: A network analysis of response to COVID-19 from the central government of China

Emergency information release during public health emergencies is a governance measure to slow down the spread of the epidemic and guide the public in scientific protection. Because of the uncertainty and life-cycle characteristics of public health emergencies, emergency information release represents the process of time dynamics. At present, it is an inevitable trend to establish a collaborative mechanism for emergency information release of public health emergencies to improve the release efficiency and respond to public demand. To determine time evolution characteristics of organizational collaboration in emergency information release, this study took the response to COVID-19 from the central government of China as an example and conducted research based on social network analysis. Based on information from COVID-19-related press conferences held by China's central government, the emergency information release collaborative networks (EIRCNs), and Emergency Organizations-Emergency Information Release Matters (EOs-EIRMs) 2-mode network were constructed. With the time evolution, the tightness, convergence, stability, and connectivity of EIRCNs in public health emergencies presented the process of lowering and then raising. At different stages, the core emergency organization (EO) nodes in EIRCNs continued to maintain a certain degree of activity. Their dynamic processes showed the characteristics of diversification rather than homogeneity. The time evolution of emergency information release matters (EIRMs) reflected the dynamic adjustment of the government's prevention and control measures and responded to the diversification of the public's understanding and protection needs during different stages of the COVID-19 pandemic. The study further examined the driving factors and implementation mechanism of the time evolution characteristics of the collaborative mode of emergency information release. The implementation of EIRMs at different stages had different resource requirements, which were usually achieved by introducing new EOs (Adding resource increment) or increasing the collaborative frequencies among EOs (Activating resource stock). In addition, further research prospects and feasibility interpretation were proposed.

A Study on the Mechanism and Strategy of Cross-Regional Emergency Cooperation for Natural Disasters in China-Based on the Perspective of Evolutionary Game Theory

Natural disasters have obvious cross-regional and compound characteristics. Cross-regional emergency cooperation for natural disasters deepens the diversification of coordination relations and the complexity of interaction modes among emergency response organizations, including horizontal and vertical organizational interactions. In order to clarify the cooperation mechanism of emergency organizations during cross-regional emergency cooperation for natural disasters and to explore the key factors that affect the cooperative relationships of emergency organizations, in this study, a game model is constructed based on evolutionary game theory, which is composed of local, neighboring, and central governments. Then, the stability of the emergency game strategy is analyzed. On this basis, a numerical simulation is used to simulate the dynamic evolution trajectory of the game system. The results show that there is an embedded mutual promotion mechanism that evolves towards a positive emergency strategy combination among the game subjects. The selection strategies of the game subjects show the characteristics of consistency and the following: enhanced cooperation efficiency between local and neighboring governments, emergency capital stock, and shared resources, therefore, guiding social emergency forces to actively participate in emergency operations. Strengthening the emergency dispatching strength of the central government and the effectiveness of central-local emergency dispatching, can support the performance of cross-regional emergency cooperation for natural disasters. Furthermore, the efficiency of cooperation between local and neighboring governments will be enhanced.

An Adaptive Low-Rank Modeling-Based Active Learning Method for Medical Image Annotation

Active learning is an effective solution to interactively select a limited number of informative examples and use them to train a learning algorithm that can achieve its optimal performance for specific tasks. It is suitable for medical image applications in which unlabeled data are abundant but manual annotation could be very time-consuming and expensive. However, designing an effective active learning strategy for informative example selection is a challenging task, due to the intrinsic presence of noise in medical images, the large number of images, and the variety of imaging modalities. In this study, a novel low-rank modeling-based multi-label active learning (LRMMAL) method is developed to address these challenges and select informative examples for training a classifier to achieve the optimal performance. The proposed method independently quantifies image noise and integrates it with other measures to guide a pool-based sampling process to determine the most informative examples for training a classifier. In addition, an automatic adaptive cross entropy-based parameter determination scheme is proposed for further optimizing the example sampling strategy. Experimental results on varied medical image datasets and comparisons with other state-of-the-art multi-label active learning methods illustrate the superior performance of the proposed method.

[microRNA-106a-5p regulated the funcation human umbilical vein endothelial cells by targeting STAT3]

Objective: To investigate the effects of miR-106a-5p on the proliferation and migration of vascular endothelial cells, and the possible target gene of miR-106a-5p in endothelial cells. Methods: Human umbilical vein endothelial cells (HUVEC) were cultured in vitro, and the expression of mir-106a-5p in HUVECs was detected by real-time fluorescent quantitative polymerase chain reaction (RT-qPCR). Cell counting kit-8 (CCK-8) and wound healing assays were used to detected the proliferation and migration of HUVECs respectively.Dual luciferase repoter assay was used to identify the possible target gene of miR-106a-5p--STAT3. Results: mir-106a-5p inhibited the proliferation function of HUVECs (F=13.62, P<0.01). And mir-106a-5p expressed the migration of HUVEC,the closure rate in the mimic group was reduced after 12 h and 24 h of scratching (49.93/31.31) (χ(2)=8.240, P<0.05), (78.87/44.80) (χ(2)=10.50, P<0.01). The direct target gene of mir-106a-5p was STAT3, and miR-106a-5p regulated the expression of STAT3 through post-transcriptionally controlling. Conclusion: mir-106a-5p could inhibit proliferation and migration of HUVEC, and the possible target gene was STAT3.

Human Umbilical Cord Mesenchymal Stem Cells: Subpopulations and Their Difference in Cell Biology and Effects on Retinal Degeneration in RCS Rats

BACKGROUND

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are potential candidates for treating retinal degeneration (RD).

OBJECTIVE

To further study the biology and therapeutic effects of the hUC-MSCs on retinal degeneration.

METHODS

Two hUC-MSC subpopulations, termed hUC-MSC1 and hUC-MSC2, were isolated by single-cell cloning method and their therapeutic functions were compared in RCS rat, a RD model.

RESULTS

Although both subsets satisfied the basic requirements for hUC-MSCs, they were significantly different in morphology, proliferation rate, differentiation capacity, phenotype and gene expression. Furthermore, only the smaller, fibroblast-like, faster growing subset hUC-MSC1 displayed stronger colony forming potential as well as adipogenic and osteogenic differentiation capacities. When the two subsets were respectively transplanted into the subretinal spaces of RCS rats, both subsets survived, but only hUC-MSC1 expressed RPE cell markers Bestrophin and RPE65. More importantly, hUC-MSC1 showed stronger rescue effect on the retinal function as indicated by the higher b-wave amplitude on ERG examination, thicker retinal nuclear layer, and decreased apoptotic photoreceptors. When both subsets were treated with interleukin-6, mimicking the inflammatory environment when the cells were transplanted into the eyes with degenerated retina, hUC-MSC1 expressed much higher levels of trophic factors in comparison with hUC-MSC2.

CONCLUSION

The data here, in addition to prove the heterogeneity of hUC-MSCs, confirmed that the stronger therapeutic effects of hUC-MSC1 were attributed to its stronger anti-apoptotic effect, paracrine of trophic factors and potential RPE cell differentiation capacity. Thus, the subset hUC-MSC1, not the other subset or the ungrouped hUC-MSCs should be used for effective treatment of RD.

Erythropoietin Protects Retina Against Ceramide 2-Induced Damage in Rat

BACKGROUND

Ceramide plays critical roles in cell proliferation, senescence and apoptosis, and is implicated in neurodegenerative diseases, etc. To clarify if ceramide plays some roles in retinal diseases, we established in vivo and in vitro retinal injury models with ceramide 2 (C2) treatment. In addition, Erythropoietin (EPO), which showed protective effects on retinal cells and blood-retinal barrier (BRB), was also tested for its protection and possible mechanism(s) in these models.

METHODS

Male Sprague-Dawley rats were divided into four groups, i.e., normal control, vehicle control, C2 treatment, and C2+EPO treatment. After intravitreal injection, the rats were examined for eye fundus, electroretinogram, histological study, and immunostaining, etc. In vitro, retinal neuronal cell line (R28) and the primary human retinal microvascular endothelial cells (HRMECs) were treated with C2, cell viability assay, transendothelial electrical resistance (TEER) and BRB-related molecules were studied to test the protective effect of EPO.

RESULTS

Intravitreal C2-treatment caused significant vision loss in rats, as reflected by reduced b-wave amplitude, increased TUNEL positive cells and GFAP immunostaining in retina. Another major retinal injury observed was BRB breakdown following C2- treatment. Such C2-induced injuries were further confirmed by in vitro study. When HRMECs were treated with C2, the TEER was significantly reduced. The mechanisms for C2 to induce such injuries might be through evidently increased expressions of the related molecules like plasmalemma vesicle-associated protein (PLVAP or PV-1), ecto- 5'-nucleotidase (CD73) and intercellular adhesion molecule-1 (ICAM-1), as observed in C2-treated R28 cells. All these injuries induced by C2 were significantly prevented by EPO both in vivo and in vitro, and its protective mechanisms here might be, in addition to neuroprotective, closely related to its maintenance of BRB integrity, through reducing the expressions of PV-1, CD73 and ICAM-1.

CONCLUSION

C2 could induce severe retinal injury, and such injuries could be effectively prevented by EPO treatment.

miR-25 Mediates Retinal Degeneration Via Inhibiting ITGAV and PEDF in Rat

BACKGROUND

Age-related macular degeneration (AMD) is the main cause of irreversible blindness in the elderly. Oxidative stress in retinal pigment epithelium (RPE) is deemed to play a pivotal role in the pathogenesis of AMD. miR-25 functions as an essential modulator in response to oxidative-stress in several cell types, but its function in RPE cells is poorly understood.

OBJECTIVE

To explore the roles of miR-25 in RPE cells and in the development of AMD.

METHODS

A rat model of retinal degeneration was induced by sodium iodate (SI). Subretinal injection of antagomiR-25 was performed for the intervention while the scramble as control. Visual responses were recorded with Electroretinogram (ERG). TUNEL assay was performed to detect apoptosis. Phagosome quantification in vivo was performed to evaluate RPE cell function. Oxygen-glucose deprivation treatment was performed to mimic in vitro oxidative stress. Gene expression at mRNA level and protein level were performed by quantitative polymerase chain reaction (qPCR) and Western Blot, respectively. The pigment epithelium derived factor (PEDF) level in the cultured medium was measured by Enzyme-linked immunosorbent assay (ELISA). The interaction between miR-25 and integrin αV (IGTAV) / PEDF 3'UTR was examined by dual luciferase assay. Chromatin immunoprecipitation (ChIP) assay was performed to examine its transcriptional regulation of miR-25.

RESULTS

Oxidative stress up-regulated miR-25 in RPE cells in very early stage, accompanied by decreased phagocytosis and reduced growth factor secretion in those cells. Such changes preceded RPE cell apoptosis and visual impairment in the SItreated rats. Furthermore, antagomiR-25 intervention effectively rescued RPE cells from degeneration in such model. The increased miR-25 was confirmed to mediate RPE degeneration through direct targeting IGTAV and PEDF. On the other hand, upstream, miR-25 was found to be up-regulated by STAT3 signaling under oxidative stress in both in vivo and in vitro models.

CONCLUSION

Our findings demonstrate that, in SI-treated rats, oxidative stress activates STAT3 signaling which up-regulates miR-25 expression, in a very early stage. The increased miR-25 then inhibits ITGAV and PEDF expressions, resulting in RPE phagocytosis dysfunction and then RPE apoptosis and visual impairment as observed in patients with AMD. These findings lead us to a better understanding of AMD pathogenesis, and suggest that miR-25 could be a potential therapeutic target for oxidative stress related RPE diseases, like AMD.

Pityriasis rubra pilaris-like erythroderma secondary to phosphoinositide 3-kinase inhibition

BACKGROUND

Phosphoinositide 3-kinase (PI3K) inhibitors are a class of small-molecule inhibitors approved for the treatment of certain leukaemias and lymphomas. Their dermatological adverse event profile is poorly described.

AIM

To characterize a rare cutaneous adverse event from PI3K inhibitors in order to help dermatologists and oncologists identify and effectively manage such eruptions.

METHODS

This was a retrospective analysis of patients receiving PI3K inhibitors referred to the Skin Toxicities Program in The Center for Cutaneous Oncology.

RESULTS

Three patients on PI3K inhibitors for treatment of malignancy developed diffuse erythroderma and keratoderma. Clinical and histopathological findings were consistent with pityriasis rubra pilaris (PRP)-like reactions. All patients improved with topical and oral corticosteroids, oral acitretin, and drug discontinuation.

CONCLUSIONS

PRP-like cutaneous eruptions may develop secondary to PI3K inhibition. Early dermatological evaluation of cutaneous toxicities to PI3K inhibitors as well as rapid initiation of disease-specific treatments may help keep patients on life-prolonging anti-cancer therapies.

Human Adipose-Derived Stem Cells Delay Retinal Degeneration in Royal College of Surgeons Rats Through Anti-Apoptotic and VEGF-Mediated Neuroprotective Effects

Stem cell therapy is a promising therapeutic approach for retinal degeneration (RD). Our study investigated the effects of human adipose derived stem cell (hADSCs) on Royal College of Surgeons (RCS) rats.

METHODS

Green fluorescent protein (GFP)-labeled hADSCs were transplanted subretinally into RCS rats at postnatal (PN) 21 days to explore potential therapeutic effects, while adeno-associated viral vector (AAV2)-vascular endothelial growth factor (VEGF) and siVEGF-hADSCs were used to aid the mechanistic dissections. Visual function was evaluated by Electroretinogram (ERG) recording. Potential transdifferentiations were examined by Immunofluorescence (IF) and gene expressions were analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Apoptotic retinal cells were detected by Terminal Deoxynucleotidyl Transferase dUTP Nick End Labeling (TUNEL) assay and the cytokines secreted by hADSCs were measured by Enzyme-linked Immunosorbent Assay (ELISA).

RESULTS

The visual function of RCS rats began to decrease one week after their eyes opened at PN week 3 and almost lost in PN 5 weeks, accompanied by the loss of retinal outer nuclear layer (ONL). Subretinal transplantation of hADSCs significantly improved the visual function 2 weeks after the transplantation and such therapeutic effect persisted up to 8 weeks after the treatment (PN 11 weeks), with 3-4 rows of photoreceptors remained in the ONL and reduced apoptosis. Consistent with these phenotypic changes, the gene expression of rod photoreceptor markers Rhodopsin (Rho), Crx and Opsin (Opn1) in RCS rats showed obvious decreasing trends over time after PN 3 weeks, but were elevated with hADSC treatment. hADSC transplantation also repressed the expressions of Bax, Bak and Caspase 3, but not the expression of anti-apoptotic genes, including Bcl-2 and Bcl-XL. Finally, substantial VEGF, hepatocyte growth factor (HGF) and pigment epithelium-derived factor (PEDF) secretions from hADSCs were detected, while endogenous Vegf expression level decreased over time in RCS rats. The treatment of AAV2-VEGF showed comparable therapeutic effects as hADSCs but siRNA knockdown of VEGF in hADSCs essentially abolished the therapeutic effects.

CONCLUSIONS

Subretinal transplantation of hADSCs in RCS rats effectively delayed the retinal degeneration, enhanced the retinal cell survival and improved the visual function. Mechanistically this was mainly due to hADSC dependent anti-apoptotic and neuroprotective effects through its secretion of growth and neurotrophic factors including VEGF. Clinical application of hADSCs merits further investigation.

Functional single nucleotide polymorphism in C20orf54 modifies susceptibility to esophageal squamous cell carcinoma

The aim of this study was to explore the association of C20orf54 functional single nucleotide polymorphism (SNP) with the susceptibility to esophageal squamous cell carcinoma (ESCC) in a northern China population. The C20orf54 SNP was genotyped by direct sequencing in 240 cancer patients and 198 controls in northern China. The results showed that drinking status, family history of ESCC, and body mass index have great influence on the risk of developing ESCC. The overall genotype frequencies of C20orf54 in ESCC patients have a significant difference with healthy controls (χ(2)  = 8.06, P = 0.018). By using C/C genotype as the reference, the C/T genotype showed a significantly decreased risk to the development of ESCC. Thus, compared with the C/C genotype, smokers, drinkers with C/T genotype significantly decreased the risk of developing ESCC. A positive family history of ESCC with C/T and T/T genotype both increased the risk of developing ESCC. Body mass index between 18.5 and 24 with C/T genotype significantly decreased the risk of developing ESCC. The present study suggests that the C20orf54 functional SNP might be associated with a risk of development in ESCC.

Effects of humoral factors on ventilation kinetics during recovery after impulse-like exercise

To clarify the ventilatory kinetics during recovery after impulse-like exercise, subjects performed one impulse-like exercise test (one-impulse) and a five-times repeated impulse-like exercises test (five-impulse). Duration and intensity of the impulse-like exercise were 20 sec and 400 watts (80 rpm), respectively. Although blood pH during recovery (until 10 min) was significantly lower in the five-impulse test than in the one-impulse test, ventilation (.VE) in the two tests was similar except during the first 30 sec of recovery, in which it was higher in the five-impulse test. In one-impulse, blood CO2 pressure (PCO2) was significantly increased at 1 min during recovery and then returned to the pre-exercise level at 5 min during recovery. In the five-impulse test, PCO2 at 1 min during recovery was similar to the pre-exercise level, and then it decreased to a level lower than the pre-exercise level at 5 min during recovery. Accordingly, PCO2 during recovery (until 30 min) was significantly lower in the five-impulse than in one-impulse test..VE and pH during recovery showed a curvilinear relationship, and at the same pH, ventilation was higher in the one-impulse test. These results suggest that ventilatory kinetics during recovery after impulse-like exercise is attributed partly to pH, but the stimulatory effect of lower pH is diminished by the inhibitory effect of lower PCO2.

Genotype of Candida species associated with different conditions of vulvovaginal candidosis

It is unknown whether strains isolated from recurrent vulvovaginal candidosis (RVVC), vulvovaginal candidosis (VVC) and asymptomatic carriers are varying or not in genotyping. Candida isolates were genotyped to determine whether specific types were associated with RVVC and VVC. A total of 97 Candida isolates from RVVC patients (n = 43), from VVC patients (n = 47) and asymptomatic carriers (n = 7) were identified by germ tube test, chlamydospore test, CHROMagar Candida and API20 system and were genotyped by polymerase chain reaction (PCR) fingerprinting employing random amplification of polymorphic DNA (RAPD) assay with nine random primers screened. The RAPD identified distinct genotypes that were shared among isolates from most different individuals. Most of the 85 C. albicans strains failed to corroborate any obvious differences in the genotypic variability in the VVC, RVVC patient groups and carriers by clustering analysis. Only a few individuals were found to harbor a distinct genotype of C. albicans isolates associated with a specific disease condition.

Outcrossing and paternity analysis of Pinus densiflora (Japanese red pine) by microsatellite polymorphism

This study employed microsatellite loci to analyse outcrossing rate and pollen dispersal in Japanese red pine (Pinus densiflora) in an isolated stand. The average offspring outcrossing rate for 29 cones was 0.955. Significant differences in outcrossing rates between offspring groups on individual branches that extended in different directions at different heights were not detected. Male parents of 874 offspring collected from the maternal tree were assessed by exclusion using polymorphisms at three microsatellite loci. Paternity analysis indicated that at least 31% of the offspring were fertilized by pollen from trees outside the stand. The average distance of pollen migration within the study stand was 68 m, with a maximum value of 325 m. There was excess mating with nearby P. densiflora trees, of which only a few were predominant pollen donors. In addition, a weakly directional bias in P. densiflora pollination was also detected in the study stand, suggesting that female strobili on a branch of the maternal tree were more easily fertilized by pollen from trees in that direction.

Distamycin A modulates the sequence specificity of DNA alkylation by duocarmycin A

Duocarmycin A (Duo) normally alkylates adenine N3 at the 3' end of A + T-rich sequences in DNA. The efficient adenine alkylation by Duo is achieved by its monomeric binding to the DNA minor groove. The addition of another minor groove binder, distamycin A (Dist), dramatically modulates the site of DNA alkylation by Duo, and the alkylation switches preferentially to G residues in G + C-rich sequences. HPLC product analysis using oligonucleotides revealed a highly efficient G-N3 alkylation via the cooperative binding of a heterodimer between Duo and Dist to the minor groove. The three-dimensional structure of the ternary alkylated complex of Duo/Dist/d(CAGGTGGT).d(ACCACCTG) has been determined by nuclear Overhauser effect (NOE)-restrained refinement using 750 MHz two-dimensional NOE spectroscopy data. The refined NMR structure fully explains the sequence requirement of such modulated alkylations. This is the first demonstration of Duo DNA alkylation through cooperative binding with another structurally different natural product, and it suggests a promising new way to alter or modify the DNA alkylation selectivity in a predictable manner.

Fluorine-19 nuclear magnetic resonance spectroscopic study of fluorophenylalanine- and fluorotryptophan-labeled avian egg white lysozymes

We report the 470-MHz (11.7 T) 19F solution nuclear magnetic resonance (NMR) spectra of 2-, 3-, and 4-fluorophenylalanine incorporated into the egg white lysozymes (EC 3.2.1.17) of chicken, pheasant, and duck, as well as spectra of 4-fluorotryptophan incorporated into chicken, California valley quail, and Bob White quail and 5- and 6-fluorotryptophan-labeled chicken lysozyme. The 19F solution NMR spectrum of [4-F]Phe hen egg white lysozyme (HEWL) consists of three sharp resonances, which span a total chemical shift range of 4.8 ppm (at p2H = 6.1). For [3-F]Phe HEWL, the chemical shift range is much smaller, 1.0 ppm (at p2H = 5.9), due presumably to the occurrence of fast phenyl ring flips about the C beta-C gamma bond axis. For [2-F]Phe HEWL, six resonances are observed, spanning a chemical shift range of 7.4 ppm (at p2H = 5.8), due to slow C beta-C gamma ring flips, i.e., both ring-flip isomers appear to be "frozen in" because of steric hindrance. Rotation of the [2-F]Phe residues remains slow up to 55 degrees C (p2H = 4.7). With the [F]Trp-labeled proteins, we find a maximal 14.6-ppm shielding range for [4-F]Trp HEWL but only a 2.8- and 2.4-ppm range for [5- and 6-F]Trp HEWL, respectively, due presumably to increased solvent exposure in the latter cases. Guanidinium chloride denaturation causes loss of essentially all chemical shift nonequivalence, as does thermal denaturation. Spectra recorded as a function of pH show relatively small chemical shift changes (< 1.4 ppm) over the pH range of approximately 1.2-7.8.(ABSTRACT TRUNCATED AT 250 WORDS)